When scheduling the initial root and when using
`unstable_scheduleHydration` we should use the Hydration Lanes rather
than the raw update lane. This ensures that we're always hydrating using
a Hydration Lane or the Offscreen Lane rather than other lanes getting
some random hydration in it.
This fixes an issue where updating a root while it is still hydrating
causes it to trigger client rendering when it could just hydrate and
then apply the update on top of that.
It also fixes a potential performance issue where
`unstable_scheduleHydration` gets batched with an update that then ends
up forcing an update of a boundary that requires it to rewind to do the
hydration lane anyway. Might as well just start with the hydration
without the update applied first.
I added a kill switch (`enableHydrationLaneScheduling`) just in case but
seems very safe given that using `unstable_scheduleHydration` at all is
very rare and updating the root before the shell hydrates is extremely
rare (and used to trigger a recoverable error).
The need for this was removed in
https://github.com/facebook/react/pull/30831
Since the new DevTools version has been released for a while and we
expect people to more or less auto-update. Future versions of React
don't need this.
Once we remove the remaining uses of `getInstanceFromNode` e.g. in the
deprecated internal `findDOMNode`/`findNodeHandle` and the event system,
we can completely remove the tagging of DOM nodes.
To avoid GC pressure and accidentally hanging onto old trees Suspense
boundary retries are now implemented in the commit phase. I used the
Callback flag which was previously only used to schedule callbacks for
Class components. This isn't quite semantically equivalent but it's
unused and seemingly compatible.
This is a hack that ensures that all four lanes as visible whether you
have any tracks in them or not, and that they're in the priority order
within the Scheduler track group. We do want to show all even if they're
not used because it shows what options you're missing out on.
<img width="1035" alt="Screenshot 2024-11-22 at 12 38 30 PM"
src="https://github.com/user-attachments/assets/f30ab0b9-af5e-48ed-b042-138444352575">
In Chrome, the order of tracks within a group are determined by the
earliest start time. We add fake markers at start time zero in that
order eagerly. Ideally we could do this only once but because calls that
aren't recorded aren't considered for ordering purposes, we need to keep
adding these over and over again in case recording has just started. We
can't tell when recording starts.
Currently performance.mark() are in first insertion order but
performance.measure() are in the reverse order. I'm not sure that's
intentional. We can always add the 0 time slot even if it's in the past.
That's still considered for ordering purposes as long as the measurement
is recorded at the time we call it.
This ensures that we mark the time from ping until we render as
"Blocked".
We intentionally don't want to show the event time even if it's
something like "load" because it draws attention away from interactions
etc.
<img width="577" alt="Screenshot 2024-11-21 at 7 22 39 PM"
src="https://github.com/user-attachments/assets/70cca2e8-bd5e-489f-98f0-b4dfee5940af">
This avoid re-emitting the yellow "Event" log when we ping inside the
original event. Instead of treating events as repeated when we get
repeated updates, we treat them as repeated if we've ever logged out
this event before.
Additionally, in the case the prerender sibling flag is on we need to
ensure that if a render gets interrupted when it has been suspended we
treat that as "Prewarm" instead of "Interrupted Render".
Before:
<img width="539" alt="Screenshot 2024-11-19 at 2 39 44 PM"
src="https://github.com/user-attachments/assets/190ca50c-5168-40d8-a6fd-6b9a583af1f0">
After:
<img width="1004" alt="Screenshot 2024-11-21 at 4 53 16 PM"
src="https://github.com/user-attachments/assets/0c441ada-1ed1-412c-8935-aaf040c25dfe">
Fixes a bug with the experimental `useResourceEffect` hook where we
would compare the wrong deps when there happened to be another kind of
effect preceding the ResourceEffect. To do this correctly we need to add
a pointer to the ResourceEffect's identity on the update.
I also unified the previously separate push effect impls for resource
effects since they are always pushed together as a unit.
Stacked on #31552. Must be tested with `enableSiblingPrerendering` off
since the `use()` optimization is not on there yet.
This adds a span to the Components track when we yield in the middle of
the event loop. In this scenario, the "Render" span continues through
out the Scheduler track. So you can see that the Component itself might
not take a long time but yielding inside of it might.
This lets you see if something was blocking the React render loop while
yielding. If we're blocked 1ms or longer we log that as "Blocked".
If we're yielding due to suspending in the middle of the work loop we
log this as "Suspended".
<img width="837" alt="Screenshot 2024-11-16 at 1 15 14 PM"
src="https://github.com/user-attachments/assets/45a858ea-17e6-416c-af1a-78c126e033f3">
If the render doesn't commit because it restarts due to some other
prewarming or because some non-`use()` suspends, it doesn't have from
context components.
<img width="971" alt="Screenshot 2024-11-16 at 1 13 55 PM"
src="https://github.com/user-attachments/assets/a67724f8-702e-4e7d-9499-9ffc09541a61">
The `useActionState` path doesn't work yet because the `use()`
optimization doesn't work there for some reason. But the idea is that it
should mark the time that the component is blocked as Action instead of
Suspended.
When we suspend the render with delay, we won't do any more work until
we get some kind of another update/ping. It's because conceptually
something is suspended and then will update later. We need to highlight
this period to show why it's not doing any work. We fill the empty space
with "Suspended". This stops whenever the same lane group starts
rendering again. Clamped by the preceeding start time/event time/update
time.
<img width="902" alt="Screenshot 2024-11-15 at 1 01 29 PM"
src="https://github.com/user-attachments/assets/acf9dc9a-8fc3-4367-a8b0-d19f9c9eac73">
Ideally we would instead start the next render and suspend the work loop
at all places we suspend. In that mode this will instead show up as a
very long "Render" with a "Suspended" period instead highlighted in the
Components track as one component is suspended. We'll soon have that for
`use()` but not all updates so this covers the rest.
One issue with `useActionState` is that it is implemented as suspending
at the point of the `useActionState` which means that the period of the
Action shows up as a suspended render instead of as an Action which
happens for raw actions. This is not really how you conceptually think
about it so we need some special case for `useActionState`. In the
screenshot above, the first "Suspended" is actually awaiting an Action
and the second "Suspended" is awaiting the data from it.
This PR introduces a new experimental hook `useResourceEffect`, which is
something that we're doing some very early initial tests on.
This may likely not pan out and will be removed or modified if so.
Please do not rely on it as it will break.
This lets us track separately if something was suspended on an Action
using useActionState rather than suspended on Data.
This approach feels quite bloated and it seems like we'd eventually
might want to read more information about the Promise that suspended and
the context it suspended in. As a more general reason for suspending.
The way useActionState works in combination with the prewarming is quite
unfortunate because 1) it renders blocking to update the isPending flag
whether you use it or not 2) it prewarms and suspends the useActionState
3) then it does another third render to get back into the useActionState
position again.
This includes:
- `Interrupted Render`: Interrupted Renders (setState or ping at higher
priority)
- `Prewarm`: Suspended Renders outside a Suspense boundary
(RootSuspendedWithDelay/RootSuspendedAtTheShell)
- `Errored Render`: Render that errored somewhere in the tree (Fatal or
Not) (which may or may not be retried and then complete)
- `Teared Render`: Due to useSyncExternalStore not matching (which will
do another sync attempt)
Suspended Commit:
<img width="893" alt="Screenshot 2024-11-14 at 11 47 40 PM"
src="https://github.com/user-attachments/assets/b25a6a8b-a5e9-4d66-b325-57aef4bf9dad">
Errored with a second recovery attempt that also errors:
<img width="976" alt="Screenshot 2024-11-15 at 12 09 06 AM"
src="https://github.com/user-attachments/assets/9ce52cbb-b587-4f1e-8b67-e51d9073ae5b">
It's useful to quickly see where new events are kicking off new
rendering. This uses the new "warning" color (yellow) to do that. This
is to help distinguish it from the purple (secondary color) which is
used for the commit phase which is more of a follow up and it's often
that you have several rerenders within one event which makes it hard to
tell a part where it starts and event otherwise.
For the span marking between previous render within the same event and
the next setState, I use secondary-light (light purple) since it's kind
of still part of the same sequence at that point. It's usually a spawned
render (e.g. setState in useEffect or microtask) but it can also be
sequential flushSync.
I was bothered by that the event name is the only thing that's lower
case so I prefixed it with `Event: ` like the JS traces are.
<img width="1499" alt="Screenshot 2024-11-13 at 7 15 45 PM"
src="https://github.com/user-attachments/assets/0c81c810-6b5d-4fc7-9bc0-d15b53844ade">
It might be a little confusing why our track starts earlier than the JS
one below in the "Main Thread" flamegraph which looks the same. That's
because ours is the start of the event time which is when the click
happens where as the Main Thread one is when the JS event loop gets
around to processing the event.
When you schedule a microtask from render or effect and then call
setState (or ping) from there, the "event" is the event that React
scheduled (which will be a postMessage). The event time of this new
render will be before the last render finished.
We usually clamp these but in this scenario the update doesn't happen
while a render is happening. Causing overlapping events.
Before:
<img width="1229" alt="Screenshot 2024-11-12 at 11 01 30 PM"
src="https://github.com/user-attachments/assets/9652cf3b-b358-453c-b295-1239cbb15952">
Therefore when we finalize a render we need to store the end of the last
render so when we a new update comes in later with an event time earlier
than that, we know to clamp it.
There's also a special case here where when we enter the
`RootDidNotComplete` or `RootSuspendedWithDelay` case we neither leave
the root as in progress nor commit it. Those needs to finalize too.
Really this should be modeled as a suspended track that we haven't added
yet. That's the gap between "Blocked" and "message" below.
After:
<img width="1471" alt="Screenshot 2024-11-13 at 12 31 34 AM"
src="https://github.com/user-attachments/assets/b24f994e-9055-4b10-ad29-ad9b36302ffc">
I also fixed an issue where we may log the same event name multiple
times if we're rendering more than once in the same event. In this case
I just leave a blank trace between the last commit and the next update.
I also adding ignoring of the "message" event at all in these cases when
the event is from React's scheduling itself.
Fixes a bug.
We're supposed to not log "Waiting for Paint" if the passive effect
phase was forced since we weren't really waiting until the paint.
Instead we just log an empty string when we force it to still ensure
continuity.
We should always log the passive phase. This check was in the wrong
place.
Previously we were showing Components inside each lane track but that
meant that as soon as you expanded a lane you couldn't see the other
line so you couldn't get an overview over how well things were
scheduled.
This instead moves all the Components into a single top-level track and
renames the previous one to a "Scheduler" track group.
<img width="1352" alt="Screenshot 2024-11-12 at 8 26 05 PM"
src="https://github.com/user-attachments/assets/590bc6d3-3540-4ee4-b474-5d733b8d8d8d">
That way you can get an overview over what React is working on first and
then right below see which Component is being worked on.
Ideally the "Scheduler" track would be always expanded since each Track
is always just a single row. Now you have to expand each lane to see the
labels but then you're wasting a lot of vertical real estate. There's
currently no option to create this with the Chrome performance.measure
extensions.
<img width="1277" alt="Screenshot 2024-11-12 at 8 26 16 PM"
src="https://github.com/user-attachments/assets/4fc39e35-10ec-4452-ad32-c1c2e6b5e1a8">
This provides less context but skips a lot of noise.
Previously we were including parent components to provide context about
what is rendering but this turns out to be:
1) Very expensive due to the overhead of `performance.measure()` while
profiling.
2) Unactionable noise in the profile that hurt more than it added in
real apps with large trees.
This approach instead just add performance.measure calls for each
component that was marked as PerformedWork (which was used for this
purpose by React Profiler) or had any Effects.
Not everything gets marked with PerformedWork though. E.g. DOM nodes do
not but they can have significant render times since creating them takes
time. We might consider including them if a self-time threshold is met.
Because there is little to no context about the component anymore it
becomes really essential to get a feature from Chrome DevTools that can
link to something with more context like React DevTools.
This reverts commit d3bf32a958 which was
part of #30983
When you have very deep trees this trick can cause the top levels to
skew way too much from the real numbers. Creating unbalanced trees.
The bug should have been fixed in Chrome Canary now so that entries
added later are sorted to go first which should've addressed this issue.
We've previously failed to land this change due to some internal apps
seeing infinite render loops due to external store state updates during
render. It turns out that since the `renderWasConcurrent` var was moved
into the do block, the sync render triggered from the external store
check was stuck with a `RootSuspended` `exitStatus`. So this is not
unique to sibling prerendering but more generally related to how we
handle update to a sync external store during render.
We've tested this build against local repros which now render without
crashes. We will try to add a unit test to cover the scenario as well.
---------
Co-authored-by: Andrew Clark <git@andrewclark.io>
Co-authored-by: Rick Hanlon <rickhanlonii@fb.com>
## Summary
We're seeing certain situations in React Native development where ref
callbacks in `<Activity mode="hidden">` are sometimes invoked exactly
once with `null` without ever being called with a "current" value.
This violates the contract for refs because refs are expected to always
attach before detach (and to always eventually detach after attach).
This is *particularly* bad for refs that return cleanup functions,
because refs that return cleanup functions expect to never be invoked
with `null`. This bug causes such refs to be invoked with `null`
(because since `safelyAttachRef` was never called, `safelyDetachRef`
thinks the ref does not return a cleanup function and invokes it with
`null`).
This fix makes use of `offscreenSubtreeWasHidden` in
`commitDeletionEffectsOnFiber`, similar to how
https://github.com/facebook/react/commit/ec52a5698e2dfea7050a0b015f0b79abfb2d81b7
did this for `commitDeletionEffectsOnFiber`.
## How did you test this change?
We were able to isolate the repro steps to isolate the React Native
experimental changes. However, the repro steps depend on Fast Refresh.
```
function callbackRef(current) {
// Called once with `current` as null, upon triggering Fast Refresh.
}
<Activity mode="hidden">
<View ref={callbackRef} />;
</Activity>
```
Ideally, we would have a unit test that verifies this behavior without
Fast Refresh. (We have evidence that this bug occurs without Fast
Refresh in real product implementations. However, we have not
successfully deduced the root cause, yet.)
This PR currently includes a unit test that reproduces the Fast Refresh
scenario, which is also demonstrated in this CodeSandbox:
https://codesandbox.io/p/sandbox/hungry-darkness-33wxy7
Verified unit tests pass:
```
$ yarn
$ yarn test
# Run with `-r=www-classic` for `enableScopeAPI` tests.
$ yarn test -r=www-classic
```
Verified on the internal React Native development branch that the bug no
longer repros.
---------
Co-authored-by: Rick Hanlon <rickhanlonii@fb.com>
This reverts commit 6c4bbc7832.
It looked like the bug we found on the original land was related to
broken product code. But through landing #31268 we found additional bugs
internally. Since disabling the feature flag does not fix the bugs, we
have to revert again to unblock the sync. We can continue to debug with
our internal build.
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## Summary
In order to adopt react 19's ref-as-prop model, Flow needs to eliminate
all the places where they are treated differently.
`React.AbstractComponent` is the worst example of this, and we need to
eliminate it.
This PR eliminates them from the react repo, and only keeps the one that
has 1 argument of props.
## How did you test this change?
yarn flow
Follows https://github.com/facebook/react/pull/31238
___
This is a partial re-land of
https://github.com/facebook/react/pull/31056. We saw breakages surface
after the original land and had to revert. Now that they've been fixed,
let's try this again. This time we'll split up the commits to give us
more control of testing and rollout internally.
Original PR: https://github.com/facebook/react/pull/31056
Original Commit:
https://github.com/facebook/react/pull/31056/commits/4c71025d8d1bd46344ad793e7ed3049d24f7395a
Revert PR: https://github.com/facebook/react/pull/31080
Commit description:
> When a synchronous update suspends, and we prerender the siblings, the
prerendering should be non-blocking so that we can immediately restart
once the data arrives.
>
> This happens automatically when there's a Suspense boundary, because
we immediately commit the boundary and then proceed to a Retry render,
which are always concurrent. When there's not a Suspense boundary, there
is no Retry, so we need to take care to switch from the synchronous work
loop to the concurrent one, to enable time slicing.
Co-authored-by: Andrew Clark <git@andrewclark.io>
We're seeing issues with this feature internally including bugs with
sibling prerendering and errors that are difficult for developers to
action on. We'll turn off the feature for the time being until we can
improve the stability and ergonomics.
This PR does two things:
- Turn off `enableInfiniteLoopDetection` everywhere while leaving it as
a variant on www so we can do further experimentation.
- Revert https://github.com/facebook/react/pull/31061 which was a
temporary change for debugging. This brings the feature back to
baseline.
When a synchronous update suspends, and we prerender the siblings, the
prerendering should be non-blocking so that we can immediately restart
once the data arrives.
This happens automatically when there's a Suspense boundary, because we
immediately commit the boundary and then proceed to a Retry render,
which are always concurrent. When there's not a Suspense boundary, there
is no Retry, so we need to take care to switch from the synchronous work
loop to the concurrent one, to enable time slicing.
Over time the behavior of these two paths has converged to be
essentially the same. So this merges them back into one function. This
should save some code size and also make it harder for the behavior to
accidentally diverge. (For the same reason, rolling out this change
might expose some areas where we had already accidentally diverged.)
We're seeing the limit hit in some tests after enabling sibling
prerendering. Let's bump the limit so we can run more tests and gather
more signal on the changes. When we understand the scope of the problem
we can determine whether we need to change how the updates are counted
in prerenders and/or fix specific areas of product code.
A slight behavior change here too is that I now mark the start of the
commit phase before the BeforeMutationEffect phase. This affects
`<Profiler>` too.
The named sequences are as follows:
Render -> Suspended or Throttled -> Commit -> Waiting for Paint ->
Remaining Effects
The Suspended phase is only logged if we delay the Commit due to CSS /
images.
The Throttled phase is only logged if we delay the commit due to the
Suspense throttling timer.
<img width="1246" alt="Screenshot 2024-09-20 at 9 14 23 PM"
src="https://github.com/user-attachments/assets/8d01f444-bb85-472b-9b42-6157d92c81b4">
I don't yet log render phases that don't complete. I think I also need
to special case renders that or don't commit after being suspended.
This tracks the current window.event.timeStamp the first time we
setState or call startTransition. For either the blocking track or
transition track. We can use this to show how long we were blocked by
other events or overhead from when the user interacted until we got
called into React.
Then we track the time we start awaiting a Promise returned from
startTransition. We can use this track how long we waited on an Action
to complete before setState was called.
Then finally we track when setState was called so we can track how long
we were blocked by other word before we could actually start rendering.
For a Transition this might be blocked by Blocking React render work.
We only log these once a subsequent render actually happened. If no
render was actually scheduled, then we don't log these. E.g. if an
isomorphic Action doesn't call startTransition there's no render so we
don't log it.
We only log the first event/update/transition even if multiple are
batched into it later. If multiple Actions are entangled they're all
treated as one until an update happens. If no update happens and all
entangled actions finish, we clear the transition so that the next time
a new sequence starts we can log it.
We also clamp these (start the track later) if they were scheduled
within a render/commit. Since we share a single track we don't want to
create overlapping tracks.
The purpose of this is not to show every event/action that happens but
to show a prelude to how long we were blocked before a render started.
So you can follow the first event to commit.
<img width="674" alt="Screenshot 2024-09-20 at 1 59 58 AM"
src="https://github.com/user-attachments/assets/151ba9e8-6b3c-4fa1-9f8d-e3602745eeb7">
I still need to add the rendering/suspended phases to the timeline which
why this screenshot has a gap.
<img width="993" alt="Screenshot 2024-09-20 at 12 50 27 AM"
src="https://github.com/user-attachments/assets/155b6675-b78a-4a22-a32b-212c15051074">
In this case it's a Form Action which started a render into the form
which then suspended on the action. The action then caused a refresh,
which interrupts with its own update that's blocked before rendering.
Suspended roots like this is interesting because we could in theory
start working on a different root in the meantime which makes this
timeline less linear.
Ricky
Sebastian Markbåge
Andrew ClarkandJack Pope
Josh Story
lauren
Jan Kassens
Sophie Alpert
Timothy YungandRick Hanlon
Sam Zhou
Sebastian "Sebbie" Silbermann